The role of the bottom and top interfaces in the 1st reset operation in HfO2 based RRAM devices

In this work, the increase on the conductive filament conductivity during the 1^st Reset operation, by using the incremental step pulse with verify algorithm, in HfO2 based 1T1R RRAM devices is investigated. A new approach is proposed in order to explain the increase of conductivity by highlighting the crucial roles played by both metal-oxide interfaces. The top metal-oxide interface (HfO2−x/TixOy) plays a crucial role in the forming operation by creating a strong gradient of oxygen vacancies in the hafnium oxide layer. The bottom metal-oxide interface (TixOyNz/HfO2−x) also creates oxygen vacancies, which strengthen the conductive filament tip near to this interface at the beginning of the 1^st Reset, leading to the reported conductivity increase. After the 1^st Reset operation the conductive filament stabilizes at the bottom interface suppressing this behavior in the subsequent reset operations.